Synthetic vision information systems (SVIS systems) are becoming more common in avionics displays. A SVIS system is one in which a terrain display is generated or rendered using data stored in a database. A SVIS system is of great value to an aircraft pilot when flying conditions such as darkness, clouds, fog or inclement weather, which prevent the pilot from seeing surrounding terrain. FIG. 10 shows a synthetic terrain rendering 72 included in a display output of an avionics display 70. One challenge in using SVIS systems is that a pilot may confuse the displayed terrain horizon with the attitude of the aircraft. In FIG. 10 the synthetic terrain horizon 74 is downwardly slanting to the right. To correct this confusion the display will also display a horizon line 76 and pitch ladder lines 78 to communicate aircraft attitude, which during level flight conditions—zero degrees pitch and zero degrees roll—appear as horizontal lines in FIG. 10. Another example of possible confusion is shown in FIG. 12, where the synthetic terrain horizon 74 of the synthetic terrain rendering 72 appears horizontal and the horizon line 76 is angled (such as in a banked turn). Even when displaying the horizon line and pitch ladder lines, there is a risk that a pilot's eye may naturally follow the movement of the displayed terrain and ignore the attitude information superimposed thereon.
Although attitude information may be overlaid upon a synthetic terrain rendering as shown in FIG. 10, the principal source of attitude information has traditionally been an attitude direction indicator (ADI) or its more modern counterpart, an electronic attitude direction indicator (EADI). For purposes of this disclosure they will be generally considered together. Although an ADI or EADI can be an independent avionics instrument, the ADI function can also be part of a Primary Flight Display (PFD) format. FIG. 11 depicts the ADI function as part of an avionics PFD format 80. In the ADI display mode, with the aircraft flying straight and level, the display is roughly divided into two regions 82, 84. The two regions use two contrasting textures, cross-hatching, or colors, such as blue and brown, to indicate sky and ground, respectively. The horizon line 76 divides the two regions. Pitch ladder lines 78, parallel to horizon line 76, provide a measurement scale for changes in aircraft pitch. A change in the roll angle of the aircraft results in a change in the angle of horizon line 76 and pitch ladder lines 78 (FIG. 13), and a corresponding change in the area covered by regions 82, 84. The change in the roll angle is also indicated by a roll pointer 87. The combination of the two regions is sometimes termed the attitude ‘sky/ground ball.’ Although the ADI is a standard, independent instrument or part of a multi-function display on nearly all aircraft, there has been a general interest in revising and improving methods of displaying information in avionics suites. Instead of many small instruments or independent display formats, advances in technology have made it possible to use a smaller number of large displays configurable to display critical flight information in an integrated and convenient manner. With respect to the current disclosure, combining the attitude information with another display would free up critical cockpit display space.
As a general rule, several parameters must be kept in mind when adding imagery or symbology to an avionics display such as a primary flight display (PFD). For example, any added elements must not obscure or cover other information displayed on the PFD. Any added elements must not distract pilots from other displayed information. Furthermore, because the display of attitude is a critical function, an avionics system should always be able to display attitude information, and should not present a misleading attitude display. Also, because most pilots expect attitude information to be presented using the traditional ADI ‘sky/ground ball’, pitch tape and roll pointer format, any new presentation of attitude information should be intuitively and immediately associated with the traditional ADI presentation. Lastly, to meet weight and space requirements for avionics systems, the generation and display of the added elements should not require additional graphics hardware, such as processors or related circuitry.
It is therefore an object of the invention to provide aircraft attitude information in a format recognizable to aircraft pilots.
It is another object of the invention to enhance the display of attitude information in avionics systems displaying synthetic terrain renderings.
It is another object of the invention to reduce independent instrumentation or display requirements in an avionics system.
A feature of the invention is the addition of an attitude cue overlaid upon a synthetic rendering of terrain such that the rendering of terrain remains substantially visible.
An advantage of the invention is that a separate instrument or display to communicate aircraft attitude information is no longer necessary.
Another advantage is that the attitude cue is designed to be intuitive to pilots familiar with the traditional ADI display.